Gases, such as nitrogen dioxide, carbon monoxide, sulfur dioxide, and ozone, are particularly harmful pollutant gases, particularly in urban and industrial areas. Since the development of governmental air quality standards, private industry and government agencies have spent considerable time and effort in the development of instruments for the detection and measurement of gaseous pollutants. However, at present there is no one gas sensing device on the market that is highly selective, low in cost and capable of continuous and reversible detection of gaseous pollutants.
Certain gas polutant sensors currently on the market, such as described in U.S. Pat. No. 3,603,954, sense the presence of oxidizable gases, such as hydrocarbons and carbon monoxide. Other sensors, such as that described in U.S. Pat. No. 3,045,198, sense the presence of gases having a Van der Waals constant above 9. While some of the current gas sensors are capable of continuous and reversible detection, the sensors are not specific to a particular gas. Furthermore, in most cases, the response rate of the sensors is slow, meaning that the element is slow to adsorb the gaseous pollutant and is correspondingly slow in releasing the gas.